Instead of color-coded Sankey arrows the different types of energy are shown with different patterns of the arrow head. We can see some typical flaws: width of the arrow changes when going from horizontal to vertical (see ‘Losses 3.24 kW’ arrow branching out to the top), flows not to scale (compare ‘Losses 3.24 kW’ arrow to ‘Losses 6.25 kW’ arrow), overemphasis of some arrows through massive arrow heads.

A retro-style Sankey diagram from the times you would hand-draw such figures.

All others can just skip and go directly to page 22 of the paper to find this Sankey diagram based on 100.000 simulation runs:

via Twitter user @ggojedap

Groups and teams are color-coded, and the wider the band in the Sankey diagram, the higher the probability. So, according to this model, which takes into account performance of the teams since 2010, a nation from the green group will become the world champion. Purple runs with a probability of 18% and red with 14% (for the detailed values that form the basis for this diagram please see table 12 on page 15 of the paper).

Well, we’ll see, and in five weeks we will know the outcome. Whether you trust this more scientific approach, or whether you would rather go with a straight-forward Paul the Octopus divination … I hope you enjoy watching the matches!

The French region Auvergne-Rhône-Alpes in the south-east of the Hexagone borders with Switzerland and Italy. Lyon and Grenoble are located in this region, known for skiing, lush pastures … and great cheese!

Given the agricultural character of Auvergne-Rhône-Alpes, biomass use for energy generation has been going strong in recent years. The agency has created energy flow Sankey diagrams for existing biogas installations, as well as a projection for the ones being under development.

Data is for 2017 and for the scenario where all projects currently under development would already completed. The yellow stream (‘déchets ménagers’) is household waste, providing 374 GWh of energy. Manure and other side-products from agriculture (green arrow) contributes another 260 GWh.
The stacked bar on the left hand side of the diagram indicates the potential availability of biomass by 2035, and one can see that only a small fraction of it is currently being taken advantage of.
Biogas is produced in anaerobic digesters (‘méthanisation’) and the region yields some 271 GWh electricity and 200 GWh heat per year from cogeneration plants. Already almost 100 GWh of biogas could be injected to the natural gas network, allowing for storage of the energy.

Note that smaller or even negligible flows are still shown with a minimum width in order to make them visible (these thinner arrows are not to scale with the others).

Among the literally hundreds of e-mails that flooded my inbox the last couple of days, urging me to consent to receiving e-mails in the future, one particularly caught my attention, since it used a Sankey diagram pic to convey the message:

My choice made clear in a simple visualization … Did I click the button? Yes I did!

This Sankey diagram depicting the energy balance of Chile for 2015 can be found on the website Gestiona Energía MiPyMEs (MiPyMEs is the Spanish term for ‘small and medium-sized enterprises’, SMEs).

Flows are in TCal (teracalories), a unit for energy we don’t get to see very often (1 TCal = 4,205 Joules). What surprised me most in this figure was that ‘Biomasa Leña’ (biomass firewood) is the third most used primary energy source. The accompanying pie chart on the same page confirms that crude oil (25%) and coal (20%) are the most important sources, followed by biomass and oil derivates (each 19%). I guess this should read ‘biomass AND firewood’ rather than ‘biomass firewood’.

Some design shortcomings, in particular where the downward sloping stacked Sankey arrow turns to run horizontally to join the node ‘Electricidad’, and at the input side of the primary energy box, where the flows for ‘Petróleo Crudo’, ‘Carbón’ and ‘Biomasa Leña’ overlap and somehow don’t seem to hold their width all the way. My guess is that this is owed to the wish to keep the figure as compact as possible.

As part of the Canadian SPRUCE-UP research project one activity is dedicated to Genomic, Ethical, Environmental, Economic, Legal or Social (GE³LS) aspects of this applied genomics project. As part of their work the scientists have developed the Canadian Forest Service – Fiber Cascade Model (CFS-FCM) simulation model.

This Sankey diagram shows one specific scenario for a downstream flow of wood fibre from Canadian forests to products. Flows are in metric tonnes (probably for one reference year), with the exception of the ‘Bioenergy’ flow, shown in terajoules (TJ).

Another Sankey diagram from the article ‘Exergoecology Assessment of Mineral Exports from Latin America: Beyond a Tonnage Perspective’ by Jose-Luis Palacios I discussed in this recent post.

Non-fuel minerals exported in 2013 from Latin America to other continents. Flows are in Mtoe (for the reason why these flows are measured with a typical energy unit and to learn about the ERC approach read the article). Due to the scale, some minerals can not be seen as individual flows in the Sankey diagram and are thus grouped as ‘Rest of Minerals’ (black stream).

Those of you who have already created Sankey diagrams might have come across the issue: As long as the flow data you are about to visualize is more or less in the same value range everything is fine, and there should be no problem in coming up with an nice Sankey diagram. However, sometimes we have very small flow quantities, while at the same time there are some large flows dominating the picture.

Sticking to the “golden rule” of Sankey diagrams (i.e. the width of the Sankey arrow corresponds to the flow quantity represented) and ensuring the proportionality of flows in relation to each other becomes very difficult. If you opt to show the larger flows at “normal” width, the smaller flows become difficult to perceive and are shown as hairlines (sometimes even invisible on a screen or in print). If, on the other hand, you decide to push up the scaling factor so that these smaller flow quantities can be seen in the diagram, then the large flows are really fat and spoil your diagram.

This seems to be an irresolvable issue… Nevertheless, there are some approaches to tackle this. Most of them resort to taking out the tiny flows or the very large flows of being to scale used in the Sankey diagram. You may opt to use a minimum width (e.g. 1 or 2 pixels) for arrows that carry only a small flow quantity, or you may decide to set an upper flow threshold, corresponding to a maximum width for the Sankey arrow, independent of the actual flow quantity (beyond the threshold value). In both cases I would strongly recommend to denote this decision in the diagram (e.g. in a footnote), since otherwise the person looking at the Sankey diagram will get a wrong idea of the quantities/proportions.

The Sankey diagram from the PROSUM report I recently featured in this post has another, quite unique solution. Here is a zoomed cropped section:

The metals in the end-of-life vehicle (ELV) stream of 8 million tons (in 2016) are mainly aluminium, copper and iron. This stream is on the same scale as the overall Sankey diagram (see full diagram here). However, the other metals in the stream (such as gold, silver or platinum) are contained in comparatively much smaller amounts. The authors of the Sankey diagram hence opted to emphasize them by switching to another scale (1:5.000). As a result the arrow representing the flow of approximately 660 tons of critical raw materials (CRMs) is almost a wide as the arrow that shows 6780 ktons!

The fact that the precious metal stream is highlighted and not to scale with the rest of the flows in the diagram is clearly signalled with a note, a dotted line that separates this diagram area, and even an exclamation mark symbol.

Since CRMs were the focus of the PROSUM study I think such a “trick” is justified. What are your experiences with flows on different scales? How would you handle this “dimension challenge” in a Sankey diagram? Let me know your ideas!